Many currently available exercise machines are designed to include an exercise arm or other member that moves in response to a force applied by the user of the machine. Typically, the exercise arm is connected to a resistance system, often a weight stack, that provides resistance to movement of the arm. Thus, as the user attempts to move the arm, the resistance system resists that movement, with the effect that the user exercises by repeatedly overcoming the resistance and moving the exercise arm.
Many exercise machines are configured so that a user can preselect certain exercise parameters. For example, if a weight stack is employed as the resistance system, the user typically can select any number of weights in the weight stack to provide resistance to movement. As a result, the user can customize an exercise routine that is best suited to the user's needs.
Some exercise machines have other features that enable a user to customize the exercise routine further. One example of such a feature is the so-called “range-limiter,” which is a device that enables the user to select the endpoints for the path the exercise arm will travel during exercise. A range limiter is particularly useful for exercise machines such as torso machines and hip-and-back machines, both of which condition and rehabilitate body regions which vary in flexibility and strength significantly between users and which are often injured, either acutely or chronically, and therefore can require limited range of motion exercise.
An exemplary and common range-limiting device, such as that illustrated in U.S. Pat. No. 5,356,360 to Johns, includes a range limiting cam that has a series of holes, any of which can receive a pin that is attached to a lever. The lever is attached to the frame of the exercise machine, and the cam is interconnected with the exercise arm. Movement of the pin to different holes determines the range of motion of the exercise device. A somewhat similar range limiter is shown in U.S. Pat. No. 5,263,914 to Simonson et al., in which range limiting capability is provided by a lever having holes that receive a limiting pin.
One shortcoming of each of these range limiters is their inability to provide “infinite” range limiting; i.e., the range of these devices is limited by the number and positions of the holes in the cam or lever. Such a machine may be unsuitable for exercisers having special exercise needs that may require the exercise machine to take a specific position that is not available with the holes offered by the lever or cam.
In addition, the range limiters of these machines are difficult, if not impossible, to adjust during exercise. As a result, a user that wishes to begin the exercise with a certain range of motion, then continue the exercise with a different range of motion, must actually cease the exercise, dismount the exercise machine, modify the range limits, remount the machine, and only then continue exercising. An exercise pattern of gradually increasing range of motion is not unusual, especially for rehabilitating exercisers who require that the portion of the body being exercised be stretched gradually to the point of full motion.
Another type of range limiter is disclosed in U.S. Pat. No. 5,104,121 to Webb, which illustrates a range limiter in conjunction with a torso exercise machine. The Webb range limiter includes a pair of sprockets mounted on a common shaft: one sprocket rotates with an eccentric cam attached to the exercise arm; and the other sprocket, which is larger than the first sprocket, rotates independently of the cam and is attached to the weight stack. A pawl having a latching tooth is attached to the larger sprocket. To establish an exercise starting position, the pawl is disengaged from the smaller sprocket via a handle, and the exercise arm is moved to a desirable starting position. The handle is then released, and the pawl is received between a pair of teeth of the smaller sprocket. The interaction between the pawl and the smaller sprocket fixes the sprockets relative to one another, which in turn connects the exercise arm and the weight stack. As a result, the relative positions of the small and large sprocket establish the starting position for the exercise arm. Although this system enables the user to select a range limit while seated in the exercise machine, it does not provide for infinite range limiting capability, as the range limits of the machine are restricted to discrete positions defined by the configuration of the sprockets and the pawl.
Another shortcoming of many exercise machines that employ cables or chains to connect the exercise arm and the weight stack is the inability of such machines to establish and maintain a constant belt tension, even when the machine is not in use. These machines should have slight tension (between 5 to 20 pounds) on the belts or chains in order to ensure that resistance is provided during the entire exercise stroke, and in particular at the beginning of the stroke. Most exercise machines of this type require periodic maintenance, during which time the belt or chain is disconnected from the weight stack. When the belts or chains are reconnected after maintenance, the tension must be re-adjusted.
Also, at times exercise machines malfunction by the lower end of the connecting rod that carries the weight becoming lodged against the top surface of the uppermost weight remaining in the weight stack. As a result, the weights connected with the connecting rod are suspended in a raised position. When this occurs, often the user will attempt to fix the problem by dislodging the lower end of the connecting rod. In response, the weights connected to the connecting rod immediately drop onto the remaining weights. As such, the user risks serious hand injury by attempting to fix the machine.